/*
* Copyright 2002-2016 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.integration.router;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import org.springframework.messaging.Message;
import org.springframework.messaging.MessageChannel;
import org.springframework.util.CollectionUtils;
/**
* A Message Router that resolves the {@link MessageChannel} based on the
* {@link Message Message's} payload type.
*
* @author Mark Fisher
* @author Oleg Zhurakousky
* @author Gary Russell
*/
public class PayloadTypeRouter extends AbstractMappingMessageRouter {
private static final String ARRAY_SUFFIX = "[]";
/**
* Selects the most appropriate channel name matching channel identifiers which are the
* fully qualified class names encountered while traversing the payload type hierarchy.
* To resolve ties and conflicts (e.g., Serializable and String) it will match:
* 1. Type name to channel identifier else...
* 2. Name of the subclass of the type to channel identifier else...
* 3. Name of the Interface of the type to channel identifier while also
* preferring direct interface over indirect subclass
*/
@Override
protected List<Object> getChannelKeys(Message<?> message) {
if (CollectionUtils.isEmpty(this.channelMappings)) {
return null;
}
Class<?> type = message.getPayload().getClass();
boolean isArray = type.isArray();
if (isArray) {
type = type.getComponentType();
}
String closestMatch = this.findClosestMatch(type, isArray);
return (closestMatch != null) ? Collections.<Object>singletonList(closestMatch) : null;
}
private String findClosestMatch(Class<?> type, boolean isArray) {
int minTypeDiffWeight = Integer.MAX_VALUE;
List<String> matches = new ArrayList<String>();
for (String candidate : this.channelMappings.keySet()) {
if (isArray) {
if (!candidate.endsWith(ARRAY_SUFFIX)) {
continue;
}
// trim the suffix
candidate = candidate.substring(0, candidate.length() - ARRAY_SUFFIX.length());
}
else if (candidate.endsWith(ARRAY_SUFFIX)) {
continue;
}
int typeDiffWeight = determineTypeDifferenceWeight(candidate, type, 0);
if (typeDiffWeight < minTypeDiffWeight) {
minTypeDiffWeight = typeDiffWeight;
// new winner, start accumulating matches from scratch
matches.clear();
matches.add((isArray) ? candidate + ARRAY_SUFFIX : candidate);
}
else if (typeDiffWeight == minTypeDiffWeight && typeDiffWeight != Integer.MAX_VALUE) {
// candidate tied with current winner, keep track
matches.add(candidate);
}
}
if (matches.size() > 1) { // ambiguity
throw new IllegalStateException(
"Unresolvable ambiguity while attempting to find closest match for [" + type.getName() + "]. " +
"Found: " + matches);
}
if (CollectionUtils.isEmpty(matches)) { // no match
return null;
}
// we have a winner
return matches.get(0);
}
private int determineTypeDifferenceWeight(String candidate, Class<?> type, int level) {
if (type.getName().equals(candidate)) {
return level;
}
for (Class<?> iface : type.getInterfaces()) {
if (iface.getName().equals(candidate)) {
return (level % 2 != 0) ? level + 2 : level + 1;
}
// no match at this level, continue up the hierarchy
for (Class<?> superInterface : iface.getInterfaces()) {
int weight = this.determineTypeDifferenceWeight(candidate, superInterface, level + 3);
if (weight < Integer.MAX_VALUE) {
return weight;
}
}
}
if (type.getSuperclass() == null) {
// exhausted hierarchy and found no match
return Integer.MAX_VALUE;
}
return this.determineTypeDifferenceWeight(candidate, type.getSuperclass(), level + 2);
}
}